Here’s a novel idea: build a wireless network of low-power HF (High Frequency – 2 to 30 MHz) radio stations to collect and transport low-speed data from remote sites.
The license granted by the FCC to HySky Technologies is intriguing. It may be unique. It grants HySky limited access to 934(!) HF frequencies. HySky’s website claims that
HySky offers an attractive alternative where cellular coverage is unavailable or , the collection of sensor data via satellites is exorbitantly expensive.
HySky boasts that its HF network will be suitable for:
- Asset Tracking
- GPS Asset Tracking
- Inland Waterways
- Hazmat Tracking
- Information Services
- Alarm and Security
- Citizen Emergency Notification
- Digital Message Sign Control
- RXR Crossing Monitoring
- Remote Sensors
- Rooftop HVAC
- Flow and Power
- Security Entry Notification
- Homeland Security
- First Responder Notification
- Citizen Notification
- Hazmat Tracking
- Container Tracking
How HF signals propagagate
HF signals behave differently than cellphone signals (which operate in the 700 to 1900 MHz range). HF signals can travel far beyond line-of-sight, either by hugging the Earth (called “groundwave”, a daytime phenomenon) or by reflecting from the ionosphere (called “skywave”). The biggest problem with HF is atmospheric and man-made noise. HF signal propagation varies not only hourly, but seasonally and as a function of the 11-year sunspot cycle.
One characteristic of HF groundwave propagation is that it is decidedly not line-of-sight: the signals permeate everywhere within a given radius. This may be an advantage relative to the directional characteristics of signals in the 700 to 1900 MHz range.
I’m going to guess that the HySky HF network will, on each link, dynamically try each of their 934 frequencies until the lowest signal-to-noise ratio (SNR) is found for that link. Apparently an out-of-band control channel will be provided by both subcarriers on broadcast FM signals and above 1 GHz signals via satellite.
HySky CEO Chief Executive Officer is Charles Maynard. I found this in Radio Ham develops HF asset tracking network:
To ensure maximum reliability, we continually test the propagation characteristics of our 954 FCC licensed frequencies within the HF radio spectrum using 44 low power transmission sites strategically located across the United States.
The mobile tracking units using this spectrum will transmit a maximum of 1 watt Effective Radiated Power using a small low- efficiency broadband antenna. The data will be received by nine stations located at low-noise [read: rural] sites across the USA which will then forward the data to customers.
An unusual network
HySky’s FCC license seems to be unique. It restricts the output power of each transmitter to 15 Watts maximum. Other license parameters: The radiated power of each HF transmitter and its antenna system(s) as typically installed must not exceed one Watt. The operational modulated emission type must be 2K80G1D. [Huh? I’ve never heard of 2K80G1D!] Maximum bandwidth is 3 kHz. The duration of each HF transmission by each transmitter must not exceed 4 seconds.
This is a very unusual system that’s now licensed and will presumably be constructed soon. I’d like to learn more about it, but can’t find many details. Can you?
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© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695